...at last we will be able to know if the RNG has a specially sympathy
to Dave. :P
Basically it's patch 3187, updated to work with current CVS (I think the only
difference is the use of gettext)
Involved changing:
* recruit_unit - location parameter is now a reference so we can
return the actual position the unit was placed at (saves O(N) search)
* all locations that call recruit_unit (but don't need the actual
position)
* turn_info::recall,::undo,::redo - added support for undoing recalls
* undo_action - added new fields for recall actions
